1. Field of the Invention
The present invention relates generally to a technology of displaying an image on a display unit of a terminal device of a computer system and, more particularly, to a method of and an apparatus for displaying the image to provide a viewer with an easy-to-see image display on a display screen.
2. Description of the Related Art
A conventional image display apparatus for displaying an image on a display unit in a computer system, a terminal device of the computer system or a terminal device of a computer-assisted system, for example, performs displaying in the following manner.
A video data generating section constructed by use of, e.g., a microprocessor unit generates video data to be displayed. The video data are temporarily written to a display video memory comprising of a RAM (Random Access Memory), viz., a V-RAM (Video RAM). The video data to be displayed are read out from the video memory in accordance with a predetermined timing. An image is displayed on a display unit. The image is also displayed on the display unit in accordance with the predetermined timing set beforehand in relation to, e.g., a characteristic of the display unit. In general, a state of a viewer, i.e., an operator is not almost taken into consideration.
On the other hand, there are circumstances when the operator does not use the terminal device, such as a keyboard, which operates an operating section for a predetermined time duration or longer. It is presumed that the operator leaves his or her seat while the terminal device is not actually employed. In such a case, if the image display through the image display apparatus is turned off, a futile consumption of the electric power can be reduced. Under such circumstances, some of the conventional image display apparatuses are constructed to stop displaying by the image display apparatus in teems of protecting, e.g., an environment. This involves detecting that, for instance, the keyboard in the terminal device is in an non-operative state for a duration of a predetermined time.
When the operator gazes at images of fine characters in the case of a text displayed on the screen, however, image scrolling or paging may be effected on the screen through operating. In this connection, if the display character image at which the operator gazes rapidly moves or changes on the screen due to, e.g., scrolling or paging, a hard-to-see state though instantaneous, is present each time. Repetitions of this state become one of the causes of eye fatigue. Further, the eye fatigue caused when this kind of repetition takes place many times frequently may induce a decline in eyesight of the operator. For example, an operator having a sound and normal eyesight may develop myopia or astigmatism. The myopia or astigmatism of the operator may get worse. Moreover, if the eyes are fatigued, as described above, the operator may suffer from a headache due to an eyestrain in some cases.
If the operator does not look at the display screen at a timing of scrolling or paging, it can be considered that the above eye fatigue is relieved. In actuality, however, it is quite difficult for the operator to deliberately close or turn the eyes away from the screen so as to seize the timing of scrolling or paging. This is, as a matter of fact, impossible.